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KMID : 0362219970240010203
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Journal of The Korean Research Society for Dental Materials
1997 Volume.24 No. 1 p.203 ~ p.211
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AGE-HARDENING CHARACTERISTICS IN A DENTAL AU-AG-CU-PD ALLOY
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Abstract
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The relationship between the isothermal age-hardening behavior and the phase transformation process in a dental casting Au-Ag-Cu-Pd alloy was investigated by means of hardness test, X-ray diffraction study.
1. The isothermal age-hardening behavior in the 350450C temperature range showed a similar tendency in the changes. However, the initial hardening was faster and the maximum hardness was higher and the overaging with softening was slower on aging at the lower temperature.
2. By the isothermal aging at 350450´C, the metastable Ag-rich al´ and AuCu I ´ ordered phases were formed from the supersaturated a phase prior to the final formation of the equilibrium Ag-rich al and AuCu I ordered phases.
3. By aging at 4500, the age-hardening was attributed to the lattice strains of the parent phases resulting from the transformation of the a phase to the metastable phases and then to the equilibrium phases.
4. By aging at 350C, the age-hardening was attributed to the lattice strains of the a phase resulting from the transformation to the metastable phases. The X-ray diffraction peaks of the a phase showed a distinct shift toward both the high and low diffraction angles during transformation.
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